A bobbin chuck, or a spindle respectively, for winding man made threads normally is supported as a cantilevered structure in a support member (e.g. in a so-called revolver head). The (maximum permissible) rotational speed of the bobbin chuck is decisive for the (maximum attainable) winding speed, which winding speed as a rule is to be maintained as constant as possible during the winding process. Depending on the length of the bobbin chuck and on the maximum diameter of the thread package (or bobbin) to be produced, an applicable range of rotational speeds results for a given design of the bobbin chuck. This application range in practical use is limited by at least one critical (natural) rotational speed at which (due to vibrations) unstable behaviour of the bobbin chuck results, i.e. a behaviour impairing or endangering safe operation of the winding assembly.
Today it is common practice that the critical rotational speed limiting the range of applications is not the lowest ("first") critical rotational speed. It is the practice in the state of the art to operate at rotational speeds above the first critical rotational speed, the first critical speed range being traversed during the speed-up of the winder.
A first solution principle is discussed with reference to U.S. Pat. No. 3,813,051; U.S. Pat. No. 3,917,182; EP-A-167708 and EP-A-234844:
A design of a bobbin chuck, or of a spindle respectively, which is supposed to avoid vibrations is shown in U.S. Pat. No. 3,813,051. On a cantilevered shaft solidly connected to the machine frame, roller bearings are provided which in turn take up a cylindrical rotatable bobbin support element. Even if the patent document (column 2, lines 6 through 11) relates to the bobbin chuck drive as well as to the friction roll drive type, the arrangement shown evidently is conceived for the last-mentioned drive type.
U.S. Pat. No. 3,917,182 (DE-A-2261709) shows a bobbin chuck provided with a chuck drive arrangement laid out in such a manner that the "critical rotational speed" (column 3, lines 41 through 45) clearly lies below the range of operating speeds of the bobbin chuck (with or without a bobbin package). This bobbin chuck comprises a rotatable central shaft supported in roller bearings located in a cylindrical cantilevered structure fixedly mounted to the machine frame.
EP-A-167708 (U.S. Pat. No. 4,575,015) shows a further development concerning another problem (namely the supply of a pressurized medium through a longitudinal duct arranged in the central shaft of the bobbin chuck) in which the arrangement of the bearings as shown in DE-A-2261709 is maintained in principle. Finally EP-A-234844 describes a method of balancing a bobbin chuck according to EP-A-167708.
A second principle of a solution is discussed with reference to U.S. Pat. No. 3,030,039, DE-A-2356014 and EP-B-217276:
U.S. Pat. No. 3,030,039 concerns a design of a bobbin chuck laid out for simultaneously winding a plurality of threads, the vibration problems not being considered in particular. The chuck is conceived as a cantilevered rotatable element. The solution shown comprises a central shaft-type spindle supported rotatably in a support member, the spindle itself serving as a support for a member comprising a cylindrical part taking up bobbin tubes. The bobbin tube clamping system is to be mounted inside the latter part.
DE-A-2356014 deals with the problems of unbalance in such structures, in particular in connection with the bobbin tube clamping system. The explanations given are scanty, but they indicate that the bobbin chuck was composed of many parts which had to be "connected" (in any manner) with the central shaft.
According to EP-B-217276 a cylindrical part of the bobbin chuck supporting the bobbin tubes is formed by a part of the shaft directly supported by the bearings. All the smaller parts of the bobbin chuck are mounted within the cylindrical element in which they can be centered against, and be held back against, the centrifugal force by the inside wall of this element. The range of application of this chuck design, for chuck lengths in excess of 1000 mm, is limited to winding speeds of less than 4500 m/min, as otherwise the second critical rotational speed would fall into the range of applications.